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High-fibre diet may protect against peanut allergy

Could a high-fibre diet reduce peanut allergies?

George Doyle/Getty

By Alice Klein

Bran lovers rejoice. Fibre-rich diets have been shown to protect against peanut allergy in mice, by increasing gut bacteria that bolster the immune system. If the same holds true for humans, our diets could prevent or even reverse allergies to peanuts.

The dramatic rise in food allergies in Western countries over the past 20 years has coincided with an increase in processed, low-fibre diets, leading to speculation that there may be a link between the two.

Now, research by Jian Tan of Monash University, in Melbourne, Australia, has backed this theory. Tan’s team has demonstrated that mice bred to have a peanut allergy are less likely to have anaphylactic reactions to peanuts if they are given a high-fibre diet than if they are on a zero-fibre diet.

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When fibre is broken down by bacteria in the intestine, it produces metabolites called short-chain fatty acids. These bind to immune cells, so they may be behind the protective effect of the diet. This theory is bolstered by the fact that previous work in mice has shown that high-fibre diets increase the types of gut bacteria that produce short-chain fatty acids from fibre.

On the fatty acid trail

To investigate further, Tan’s team bred mice that were missing short-chain fatty acid receptors on their immune cells. Sure enough, these mice were no longer protected against their peanut allergy when fed high-fibre diets. They also had impaired activity in immune cells known to play a role in food tolerance.

Cause or effect?

Another study has shown that more than 80 per cent of children with peanut allergies no longer responded badly to them, if they are given a type of bacteria that produces short-chain fatty acids while peanuts are gradually reintroduced into their diet.

The link between diet, gut bacteria and food allergy is strengthening, but many questions remain, says David Martino of Murdoch Childrens Research Institute in Melbourne. “We know that faecal microbiota is altered in kids with food allergy,” he says. “But we’re not quite sure if the altered bacteria cause the condition or are caused by it.”

Another question is whether mothers can protect their infants from food allergies by eating a high-fibre diet themselves, says Tan. “Young babies don’t eat fibre or other solids, but we know that short-chain fatty acids can be transferred via breastfeeding.”